The consumption of electricity has to be perfectly matched with generation of electricity at any moment in time. This balance is necessary in any electricity grid to maintain a stable and safe electricity supply. Energy storage can help deal with fluctuations in demand and generation by allowing excess electricity to be ‘saved’ for periods of higher electricity demand.
Energy storage can contribute to a better use of renewable energy in the electricity system since it can store energy produced when the conditions for renewable energy are good but demand may be low.
Indeed there is a need for effective way of storing electricity.
Examples of existing technologies for electrical energy storage are: batteries, the combination of fuel cells and electrolysers, supercapacitors, flywheels, superconducting magnets, compressed air and pumped hydroelectric storage. Within these technologies development of supercapacitors for cost-effective energy storage are one of the most promising technologies for providing an effective way of storing electricity. The term supercapacitor, also known as ultracapacitor, electrochemical capacitor or electrical double-layer capacitor (EDLC), covers a wide range of different devices.
A supercapacitor is a special class of capacitors characterized by extremely high specific capacitances compared to regular capacitor. Traditionally supercapacitors achieve extremely high specific capacitances by utilization of charge storage in the double-layer interface between a porous electrode and a liquid electrolyte solution. This technology has several advantages over batteries and other common technologies for storage of electrical energy where extremely high power density and long device life time are some of the most important. The high power density of supercapacitors gives them an ability to be charged much faster than batteries and it allows them to deliver much more power to a load compared to a similar sized battery.
Typically supercapacitors have higher power density, cyclability, shelf life and energy efficiency but lower energy density than batteries. Because of these attributes there are several applications where supercapacitors are preferred over batteries especially because of their ability to charge and discharge much faster than batteries. However, their lower energy density can be problematic especially for mobile applications and finding ways of increasing this is therefore an important research goal. For stationary applications on the other hand the energy density is less important in itself and instead parameters like energy storage economy both during operation and overall in the life time of the device are more important. Because of supercapacitors high energy efficiency and operational life time they have potential to become a very cost-effective energy storage technology. Evaluation of the total storage economy of a device is not a trivial matter but generally it must be the ratio between the cost saving due to recovered electrical energy and the cost of the device. The long service life of a supercapacitor means that more electricity can be stored during its lifetime and its high energy efficiency means that a high degree of the stored electricity is recovered.
Therefore there is a need for developments of supercapacitors to maximize storing capacity and minimize costs.